Autonomous vehicles use various computing systems to aid in the transport of passengers from one location to another. Some autonomous vehicles may require some initial input or continuous input from an operator, such as a pilot, driver, or passenger. Other systems, for example autopilot systems, may be used only when the system has been engaged, which permits the operator to switch from a manual mode (where the operator exercises a high degree of control over the movement of the vehicle) to an autonomous mode (where the vehicle essentially drives itself) to modes that lie somewhere in between.
A vehicle may be equipped with various types of sensors and receivers in order to detect the location of itself and objects in its surroundings. For example, an autonomous vehicle may include lasers, sonar, radar, cameras, global positioning units, and other devices which pinpoint the location of the vehicle. These devices alone or in combination may be used to both build 3D models of the objects detected in the vehicle's surrounding and orient the vehicle with its surrounding. A vehicle traveling in a 3D environment, however, may rely on a 2D map. As such, it may be difficult for the vehicle to know exactly where it is located if the vehicle is, for example, traveling underneath an overpass.